TRIAL OF STANDARD VERSUS MODIFIED EXPIRATION TO ACHIEVE END-OF-TEST SPIROMETRY CRITERIA

To assess whether satisfying American Thoracic Society (ATS) end-of-te st spirometry criteria can be enhanced by modifying the patient's expi ratory technique, we conducted a cross-over trial of two expiratory te chniques in 48 patients with a range of pulmonary functions (Group 1, n = 12: FEV1/FVC < 0.45; Group 2, n = 11: FEV1/FVC, 0.45 to 0.60; Grou p 3, n = 16: FEV1/FVC, 0.61 to 0.74; Group 4, n = 9: FEV1/FVC greater- than-or-equal-to 0.75). After randomizing the order of testing, each p atient performed three exhalations using a ''standard'' forced expirat ory maneuver and a modified expiratory technique consisting of an init ial maximal expiratory effort followed by a ''relaxed expiration'' for as long as possible. Patients initiated ''relaxed expiration'' when i nstructed by the supervising technician, who issued the instruction to relax when expiratory airflow fell to less-than-or-equal-to 200 ml/s (as determined by flow-volume loop analysis). ATS end-of-test criteria were satisfied significantly more often using the modified expiratory technique (58.3% of testing sessions) than using the standard techniq ue (18.7% of sessions, p = 0.001) because of prolongation of the force d expiratory time (FET) with the modified technique in all patient gro ups. In the 38 patients with FEV1/FVC less-than-or-equal-to 0.75, the largest FVC and FET rose significantly using the modified expiratory t echnique, without compromising the largest FEV1 in any group. In patie nts with FEV1/FVC greater-than-or-equal-to 0.75, FET increased without concomitant changes in FVC or FEV1. Comparability of initial expirato ry efforts during the ''effort-dependent'' portion of expiration was a ssured because largest peak expiratory flow rate measurements were sim ilar during standard and modified testing. We conclude that: (1) a mod ified expiratory technique can enhance satisfaction of ATS end-of-test criteria; (2) in patients with airflow obstruction, FVC and FET can b e increased using the modified expiratory technique without lessening FEV1; and (3) subjective ratings by patients showed a nonsignificant t rend favoring the modified technique.